Electromagnetically actuated valve

ABSTRACT

Electromagnetically actuated valve, comprising an actuating device, a movable plunger and a valve chamber with an opening for the medium passing through it, which opening may be closed by the plunger. In order to ensure safe functioning of the valve at small closing forces, the valve chamber is totally sealed against the actuating device and the movable plunger by means of a flexible diaphragm, the diaphragm being fitted into the housing along its circumference and being pressed against the edge of the opening by the movable plunger.

BACKGROUND OF THE INVENTION

The invention relates to an electromagnetically actuated valvecomprising an actuating device, a movable plunger and a valve chamberwith an opening for the medium passing through it, which opening can beclosed by means of the plunger, and further comprising a flexiblediaphragm completely sealing the valve chamber against the actuatingdevice and the movable plunger, which diaphragm is fitted into thehousing and may be pressed against the edge of the opening by means ofthe movable plunger.

In general, such valves are used with media loaded with solid matter oraggressive media, for instance waste water.

DESCRIPTION OF THE PRIOR ART

A description of such a valve is given in U.S. Pat. No. 3,812,398, theplunger and actuating device of this valve being sealed against thedirty water with the use of a diaphragm. This diaphragm is configured asa kind of bellows surrounding the plunger partially in axial direction.Since the entire diaphragm is located in the liquid stream, thearrangement requires back-up rings in order to prevent the bellows fromcollapsing. For this reason this kind of diaphragm is a complex,expensive and failure-prone component. In the instance of stronglypolluted media the folds of the bellows may become caked with deposits,which will further impair the functioning of the valve and increase itswear.

In EP-A 0 373 142 a tube valve is disclosed which is actuated by abistable magnet. In this instance no problems will arise with pollutedmedia, as the medium will remain within the closed tube. In order toensure that the valve is closed fully even at medium pressures of up to10 bar, the holding and closing forces required for such valves arecomparatively large. This will necessitate a large, heavy and thusexpensive magnet on the one hand, and a relatively high energyexpenditure for the switching process on the other hand.

SUMMARY OF THE INVENTION

It is an object of the invention to avoid the above disadvantages and topropose an electromagnetically actuated valve, which is also suitablefor use with polluted media and whose energy expenditure for switchingis as low as possible.

In the invention this object is achieved by providing an essentiallydisk-shaped diaphragm which is attached to the housing along itscircumference. In this instance the diaphragm has a two-fold function,i.e., that of a sealing element sealing the elements of the actuatingdevice and the plunger against the medium, and that of an actual closingelement.

Energy consumption is particularly low if the plunger has two extremepositions both of which are stable. In the case of the so-calledbistable magnets energy is required only for the switching between theextreme positions. Both in the open and in the closed position of thevalve the plunger is held by a permanent magnet, a spring or the like.

A low-energy and low-noise variant of the invention is obtained bykeeping the movable plunger in one of its two stable positions by meansof a permanent magnet, the plunger being provided both with a pole faceand with a stop face preferably furnished with a damping pad, which stopface will determine one extreme position of the plunger together with acorresponding counter face in the housing, a device being provided inthe area between the pole face of the plunger and a fixed pole facecooperating with the first pole face, for the purpose of bridging theair gap between these pole faces and transmitting the magnetic flux. Asthe magnetic forces are strongly dependent on distance, the plunger isstrongly accelerated during the switching process by conventionalbistable magnets, and hits the permanent magnet or a pole plate placedbetween permanent magnet and plunger at comparatively high velocity.This will cause vibrations and considerable noise, which is oftenundesirable. In order to dampen the impact the flange bearing the stopface may be made of plastics material. If this is consideredinsufficient, an additional damping pad may be provided.

Other known variants of bistable magnets attempt to evade this problemby adding a pad of flexible material between the plunger and the magnetor pole plate in order to absorb the impact shock. Although thisarrangement will help to solve the noise problem, it will create a gapfor the magnetic lines of flux, thus reducing the holding forcesconsiderably. In the version described by the invention a damping padwill guarantee quiet operation free of noise and vibrations. Between thepole faces a gap will remain, which will depend on the required closingforces of the valve and the state of wear of the damping pad, and whichmay therefore vary in size. This gap is bridged, however, by the devicetransmitting the magnetic flux, and a great holding force is thusensured.

In a particularly advantageous variant the permanent magnet will holdthe plunger in its extreme position corresponding to the open valve, anda spring is provided which will hold the plunger in its other extremeposition. In this manner a particularly simple magnet configuration isobtained.

The device transmitting the magnetic flux may be configured in varioussuitable ways, i.e. as an annular short-circuit plate assuming a tiltedposition when the plunger is in extreme position,, or as a soft helicalspring of ferromagnetic material, or as a short-circuit pin capable ofmoving parallel to the direction of travel of the plunger. For practicalpurposes the variant most suitable for a particular application may beselected.

Especially low switching forces are obtained by giving the diaphragm anessentially circular shape and by providing it with an annular region ofreduced thickness around the central region facing the edge of theopening to be closed. The central part of the diaphragm serving as theactual closing element must have a certain--relatively large--thicknessto perform its function satisfactorily. If the entire diaphragm is giventhis uniform thickness, the plunger must not only overcome the pressureforces of the medium as the valve closes, but it must also perform aconsiderable amount of deformation work on the diaphragm. By reducingthe thickness of the diaphragm in the area subject to the strongestdeformation during the switching process, this deformation work can bedrastically reduced. The larger material thickness at the periphery ofthe diaphragm, i.e., where it is fastened to the housing, and near theopening to be closed, which is necessary for mechanical reasons, ismaintained.

In a preferred variant of the invention the proposal is put forward thatthe interior of the actuating device be filled with a fluid, preferablyoil. In this way no forces of pressure need to be surmounted during theswitching process, which will keep the size of the actuating deviceespecially small and ensure very low energy expenditure duringoperation. Besides, the movement of the plunger is cushioned by the oilfilling and noise is further reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described by way of example only withreference to the accompanying drawings, in which

FIG. 1 gives a section of a valve and its actuating device as describedby the invention,

FIGS. 2, 3, 4, 5 give sections of further variants of the invention,with the valve open,

FIG. 6 gives the variant of FIG. 5, with the valve closed.

FIGS. 7 to 11 give different variants of the device bridging the air gapbetween the pole faces and transmitting the magnetic flux.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the valve presented in FIG. 1 the valve base 1 has an essentiallydisk-shaped valve chamber 2, which is provided with an inlet bore 3 andan outlet bore 4. The housing 5 of the actuating device 6 isscrew-mounted in the valve base 1. Between the valve base 1 and thehousing 5 a flexible diaphragm 7 is held, which seals the valve chamber2 against the actuating device 6. The actuating device 6 holds a movableplunger 8, which is capable of pressing the diaphragm 7 against theopening 9 of the outlet bore 4.

The plunger 8 is surrounded by a tubular body 10 made of ferromagneticmaterial. This plunger 8 may be made of plastics. A spring 12 is used topress the plunger 8 into the position corresponding to the closed valve.Switchover is effected with the use of an electromagnet 13, which isprovided with a housing 13a, 13b. On the distant end of the valve theactuating device 6 contains a permanent magnet 17 attracting the body 10of the plunger 8 against the action of the spring 12. Between theplunger 8 with its tubular body 10 and the permanent magnet 17 a poleplate 16 is located, which is made of magnetically conductive material.In order to be able to bridge a potential air gap between the pole face31a of the tubular body 10 and the pole face 31b of the pole plate 16, amagnetically conductive short-circuit plate 15 is placed between theseelements, which is held in place by a sleeve 14, which in turn ispermanently attached to the pole plate 16. The magnetically conductiveshort-circuit plate 15 can move against the sleeve 14 to a certainextent. In this way the magnetic circuit from the permanent magnet 17 tothe pole plate 18, the cover plate 19, the housing 13b, the cover plate11, the tubular body 10, the magnetically conductive short-circuit plate15 and the pole plate 16 is closed. Housing 5 is closed by a lid 20.

In the area of the valve base 1 the plunger 8 is provided with a flange21, whose side facing away from the valve has a stop face 22a coveredwith a damping pad 23. When the valve is opened the movement of theplunger 8 is limited by the stop face 22a and its damping pad 23touching the counter face 22b located on the cover plate 11 opposite ofthe stop face 22a. The cover plate 11 rests against the housing 13a ofthe electromagnet 13. A particularly long life of the diaphragm 7 isobtained if the geometry of the components permits a further face 33a ofthe flange 21 to rest against a shoulder 33b of the housing 5 in theclosed position of the valve. In this way deformation of the diaphragm 7as regards its wall thickness may be checked.

The variant shown in FIG. 2 differs from the one above only in that thediaphragm 7a has a central part 24 facing the opening 9, which is usedfor closing this opening. This central part 24 is surrounded by athin-walled area 25, which is deformed when the valve is closed. Thethin-walled area 25 in turn is surrounded by the fastening area 26,whose wall thickness is larger again to ensure proper sealing betweenthe valve base 1 and the housing 5.

FIG. 3 presents a variant in which the diaphragm 7b has a thick-walledcentral part 24b made of hard material, which is surrounded by athin-walled area 25b of a lower Shore hardness than the central part24b. The Shore hardness of the fastening area 26b is higher again. Sucha diaphragm 7b can be made by two-polymer injection molding, forexample. In order to reduce the required closing forces amushroom-shaped body 27 is used as a closing element in the center ofthe diaphragm 7c in FIG. 4, which element is separated from theremaining diaphragm 7c by a constriction 28. This constriction 28 servesas a pressure relief zone, since the inner pressure in the valve chamber2 will now act on a much smaller area. The plunger 8 must be providedwith a tip 29 of reduced cross-section in the area of the diaphragm 7c.

FIG. 5 shows a valve whose diaphragm 7a is totally relieved frompressure. The diaphragm 7a corresponds to that of the variant presentedin FIG. 2. Unlike in FIG. 2, however, the chamber 30 behind thediaphragm is filled with an incompressible fluid in this instance, forexample with oil; because of the flexibility of the diaphragm 7a thepressure in chamber 30 is always the same as that in chamber 2. In FIG.5 the valve is shown in its open state. When the plunger 8 moves intoclosing position the diaphragm 7a is deformed accordingly in order to beable to maintain the pressure balance between the chamber 30 and thevalve chamber 2. FIG. 6 gives a detail showing how the diaphragm 7a maybe deformed.

FIG. 7 gives a detailed view of a magnetically conductive short-circuitplate 15. The magnetically conductive short-circuit plate 15 is centeredby a sleeve 14 and is freely movable within the given structuralconstraints. When the plunger 8 with its tubular body 10 approaches thepole plate 16 in the open position of the valve, the magneticallyconductive short-circuit plate 15 is tilted, forming a metal connectionbetween the tubular body 10 and the pole plate 16. This will lead to aconsiderable increase in magnetic flux. An O-ring 15a is held in agroove of the magnetically conductive short-circuit plate 15, whichserves as a sound-absorbing element when the magnetically conductiveshort-circuit plate 15 hits the pole plate 16. In the variant shown inFIG. 8 the magnetic short-circuit plate 15 will deform due to the effectof the magnetic forces, assuming a slightly conical shape. To facilitatethe deformation of plate 15 a number of radial slits are provided. Theindividual segments separated by these slits are connected by bridges32. These bridges 32 may be omitted such that the individual segmentsare held together only by the O-ring 15a.

As is shown in FIG. 9, the magnetic contact may also be established viaa stack of short-circuit laminations 15b, which are located between thepole plate 16 and the tubular body 10.

In the variant of FIG. 10 a soft helical spring 15c of ferromagneticmaterial is used for the transmission of magnetic flux.

In FIG. 11 the transmission of magnetic flux is effected byshort-circuit pins 15d moving axially.

I claim:
 1. An electromagnetically actuated valve with a valve chamber,comprisingan actuating device, a movable plunger, a valve chamber withan opening for a medium passing through it, which opening can be closedby means of said plunger, and a flexible disk-shaped substantially flatdiaphragm completely sealing said valve chamber against the actuatingdevice and said movable plunger, which diaphragm is fitted into thehousing and may be pressed against the edge of the opening by means ofsaid movable plunger, and which diaphragm is attached to a fixed part ofthe valve along its circumference, said plunger having two extremepositions which are both stable, wherein a permanent magnet is providedto hold said movable plunger in one of its two stable position, saidplunger being provided with both a pole face and a stop face which stopface will determine one extreme position of said plunger together with acorresponding counter face in the housing, a device being provided inthe area between the pole face of said plunger and a fixed pole facecooperating with the pole face of the plunger, for the purpose ofbridging the air gap between the pole faces and transmitting themagnetic flux.
 2. An electromagnetically valve according to claim 1,wherein said plunger is held by the permanent magnet in its extremeposition corresponding to the open valve, and wherein a spring isprovided which will hold said plunger in its other extreme position. 3.An electromagnetically actuated valve according to claim 1, wherein thedevice transmitting the magnetic flux is configured as an annularshort-circuit plate assuming a tilted position when said plunger is inextreme position.